In mobile communication, multi-antenna communication technology refers to a technology of performing modem signal processing using two or more antennas. A need for not only a multimedia communication service requiring a high quality and a very high capacity but also a high quality voice service similar to or higher than a wired communication voice quality is increasing. A core technology expected to satisfy such requirements is multi-antenna communication technology.
Multi-antenna communication technology can be divided into three types: a beam forming technology, a diversity technology, and a multiplexing technology. Beam forming technology improves performance by removing surrounding interference by adjusting phase information for each antenna to control signal strength according to the position angle between a base station and a user. Diversity technology improves performance by setting a predetermined distance between antennas to allow the antennas to independently transmit signals. A typical example of the diversity technology is a multiple input multiple output (MIMO) antenna. Multiplexing technology is a technology for transmitting different data to each of a plurality of antennas, and is used to improve the maximum transfer speed.
FIG. 1 illustrates the structure of a conventional base station antenna. Referring to FIG. 1, the conventional base station antenna includes an array antenna 10 for transmitting or receiving signals, an active portion 20 for managing amplification of a power signal, and a modem portion 30 for supplying a signal in a base band or RF band to the active portion 20 and modulating and demodulating signals.
However, since the operation of each of a plurality of element antennas 12 or a sub-array antenna constituting the array antenna 10 cannot be separately controlled, the array antenna 10 does not have a reconstruction function to control an effective opening surface of the array antenna 10 and a function to control the steering of an antenna beam. Also, since transmitting and receiving functions cannot be selectively switched, the efficiency of the array antenna 10 is low.
Therefore, for an existing base station antenna, in terms of communication, an adaptive response to a change in communication environment such as an increase or a decrease in the number of subscribers in an area after the initial installation is not possible. Also, a conventional array antenna as illustrated in FIG. 1 is not appropriate for a next generation communication environment in which a MIMO antenna is required.